Try this: Click the menu button, then click Help => Troubleshoot Mode. Restart in troubleshoot mode and check if the page crashes continue.
If they stopped, then the problem is most likely one of your extensions. You can then start in normal mode and try to disable all your extensions and then turn them on one at a time while you check if the problem reappears.
Read more about the troubleshoot mode:
https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems
If you still have the problem in Troubleshoot Mode you can try to refresh Firefox by typing this in the address line: about:support and then click the Refresh Firefox button.
Read more about what a refresh does:
https://support.mozilla.org/en-US/kb/refresh-firefox-reset-add-ons-and-settings